Extend flags passed to Trace::Start to also specify the clock source am: fbf4bd2f8d

Original change: https://android-review.googlesource.com/c/platform/art/+/2392999

Change-Id: Ib3b3ef6937ba1933b3e20341f85e9f33d0cbe8e4
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>